1. Field of the Invention
The present invention relates to a file downloading apparatus and method of a cable modem that is capable of shortening the time required for initializing a cable modem by downloading a file for initializing the cable modem.
2. Description of the Background Art
Recently, as the number of high-speed ethernet users increase, in order to provide a data communication service at a high speed, which has been provided by using a telephone network, a cable modem for relaying a data communication by using a coaxial cable installed at each home has been proposed.
The cable modem is a device for transmitting and receiving various data such as an Internet data at a high speed by using a cable TV network, which connects a user personal computer and the cable TV network.
Though an international standard for the cable modem has not been set yet, there are multimedia cable network standard (MCNS)/data over cable service interface specification (DOCSIS) modem which is widely adopted for use in Korea and the North America and a DAVIC modem which is widely used in Europe, and an IEEE modem.
Generally, a DOCSIS-authenticated cable modem has advantages that it is capable of transmitting a data at the high speed of the maximum 41 Mbps/sec. for downloading and the maximum 3 Mbps/sec in uploading (on the basis of DOCSIS 1.0) compared to the case of transmitting a data through the telephone line, and there is no charge for occupation of the telephone line even though the power is kept turning on.
The network using the cable modem will now be described in detail with reference to FIG. 1.
FIG. 1 is a drawing illustrating a network using a general cable modem, which includes a wideband communication network 10 having a plurality of servers to transmit a data to a user; a cable modem termination system (CMTS) connected to the wideband communication network 10, for transmitting and receiving a data; a cable modem (CM) 40 for receiving a data signal from the cable modem termination system 20 and transmitting it to an instrument such as a CRT 50 which can be viewed by a user; and a cable modem network manager 30 for managing data transmission and reception between the cable modem 40 and the cable modem termination system 20.
The cable modem termination system 20 includes a propagation relay (headend) unit for receiving an upstream signal transmitted from the cable modem 40 of each home and transmitting a downstream signal to the cable modem 40 of each home.
When the downstream signal is transmitted from the dable modem termination system 20, an media access control management message, a cable media control signal commonly used for several cable modems 40, is also transmitted by being included in the downstream signal, so that the cable modem 40 determines an operation method for receiving and initializing the MAC management message.
The method in which the cable modem 40 receives the downstream signal from the cable modem termination system 20 and selects an upstream channel will now be described with reference to FIG. 2.
FIG. 2 is a flow chart of a method for initializing the cable modem in accordance with the conventional art.
First, the cable modem 40 detects a downstream channel through which it can transmit and receive a data to and from the cable modem termination system 20 (step S1).
The synchronization message for synchronizing the cable modem 40 and the cable modem termination system is first received among the MAC management message transmitted from the cable modem termination system 20 through the detected downstream channel (step S2).
If the cable modem 40 and the cable modem termination system 20 are synchronized according to the synchronization message, the cable modem 40 receives an upstream channel descriptor (UCD) message having inforation related to the upstream channel from the cable modem termination system 20 through the downstream channel (step S3).
The UCD message provides information related to the upstream channel according to a plurality of servers, so that the cable modem 30 receiving one downstream can use the servers 11, 12 and 13 of the wideband communication network 10.
The cable modem 40 receives every UCD message which can be received from the selected downstream channel, selects an arbitrary one upstream channel among the received UCD message (S4), and performs a ranging process for the selected upstream channel (step S15).
The ranging is to exchange a data such as a power level and a timing synchronization between the cable modem 40 and the cable modem termination system 20 for a proper data transmission.
When the ranging process is successfully completed, the cable modem 40 receives various configuration information to be used by the cable modem 40 from the external dynamic host configuration protocol (DHCP) server 11 through the cable modem termination system 20, by using the DHCP (step S6).
The data received from the DHCP server 11 can be described in detail with reference to FIG. 3.
FIG. 3 is a drawing illustrating a format constructed by an encoding method of a general DHCP.
The data received from the DHCP server 11 includes an IP address to be used by the cable modem, an IP address of a trivial file transfer protocol (TFTP) server, an IP address of a time of day (TOD) server, and a configuration file name.
The cable modem 40 detects an IP address to be used and time and data information transmitted from the TOD server 13 by using the data received from the DHCP server (step S7), and downloads a configuration file having defined parameter values in which a data transmission/reception method with respect to the cable modem termination system 20 is defined (step S8).
The cable modem 40 performs a registration process using the downloaded configuration file. By performing the registration process, the user personal computer can transmit various information such as the Internet data to a different network and receive various information data from an external network (step S9).
In order to perform the registration process, the conventional cable modem 40 should first perform the process for downloading the configuration file every time before transmitting or receiving a data, and then, the normal operation of the cable modem can be guaranteed.
However, in the substantial cable modem network, the same configuration file is used for every cable modem domain. The change period of the configuration file is set long, and only in case that the cable modem network situation is changed, the configuration file is changed.
Accordingly, it is ineffective to download the configuration file every time when the cable modem is initialized, and since the time required for initializing the cable modem is lengthened, a delay occurs in accessing the communication network.